I actually do really believe that environment has a (potential) impact, perhaps particularly on the 2e kid.
I have three DDs. My eldest was first tested at 7.5years, educationally & emotionally she was at her lowest low. Her WISC index scores ranged between the 13th and 96th. Those scores reflected innate weakness in WMI, and that she was very bright. But I look back and wonder about what she would have scored before she started school and her wheels fell off. At 9.5 years old, 2 yrs later, after much better educational fit and much intervention, she scored FSIQ of 131 on the sb5 with visual/spatial at 135 or 136 and a WMI weakness. Would she have improved or futher declined without the vast improvement in school fit AND intervention? Will she keep rising? Will she maybe even get back to where it looked like she was headed as a an under 5?
It wasn't just about anxiety or depression, it was also about stopping developing in the expected way - and starting again. Equally I look at my 2nd DD, with the FSIQ of 146 (at 5.5 yrs) and I wonder where she's headed.
